how is it possible to curve fitting Fourier series to more than 8 series part ?

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how is it possible to curve fitting Fourier series to more than 8 series part ?

i try this programmatic but i get not the same coefficient value and the fitting is not so good

%% Create a Fourier series

    AnCosWnx='A0';
    BnSinWnx='';
    lower=1;
    upper=1;
    startpoint=0;

  for n=1:9



   LCos=AnCosWnx;
   LSin=BnSinWnx;

       ACosWx=strcat('A',num2str(n),'*cos(w*',num2str(n),'*x)');
    AnCosWnx=strcat(LCos,'+',ACosWx);
      BSinWx=strcat('B',num2str(n),'*sin(w*',num2str(n),'*x)');
   BnSinWnx=strcat(LSin,'+',BSinWx);

   Fx=strcat(AnCosWnx,BnSinWnx);


   end

  %% build the fit  function

    options = fitoptions(Fx);


   lower=zeros(1,2+n*2);
   upper=zeros(1,2+n*2);
   startpoint=zeros(1,2+n*2);

  lower(1:end)=-inf;
   upper(1:end)=inf;
  startpoint(end)=6.17*10^-3;

    set(options,'Lower',lower,...
   ;Upper',upper...
   ,;StartPoint',startpoint...
   ;Algorithm','Trust-Region');


   %% convert the output string to function


     Foutput= strcat('@(x)',output);

     Fout=  regexprep(Foutput,'\r\n|\n|\r','')
   g=str2func(Fout);
   hold on 
   h_ = plot(sat,g(sat),'r')